Method reference to replace lambda expressions

Sometimes don’t even need lambda via method reference

Following up with my previous StreamLambda post Let’s look at the previous lambda expression for map operation

Function<Song,String> getGenre = song->song.getGenre();

Instead of spelling this, you can point the compiler to a method that does the operation we want, using a method reference.

아무거나

Example of method reference

For example, Comparator! There are a lot of helper methods on the Comparator interface that, when combined with a method reference, let you see which value is being used for sorting and in which direction.

To sort songs from oldest to newest with lambda:

List<Song> result = allSongs.stream()
  .sorted((o1,o2)->o1.getYear()-o2,getYear())
  .collect(toList());

But with method reference with Comparator’s static helper method:

List<Song> result = allSongs.stream()
  .sorted(Comparator.comparingInt(Song::getYear))
  .collect(toList());